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CastCheck methodology v0.2 · data through 2026-08-30

Boston Logan · GraphCast (IFS init) · lead day 2

KBOS · graphcast_ifs · lead 2

Target day = initialization date + 2 days. This page is a permanent link: the numbers change as history accumulates, the address and the methodology version do not.

Scores use the latest model version segment, GRAP_v100, starting 2026-01-01 — days before that ran a different version of the model and are excluded rather than silently pooled. Of the scored days, 1 carry a QC flag on the observation.

JSON for this page CSV of the daily errors Cite this page

Every number for this combination

All four windows × both initializations × both interpolations × both variables. Errors are computed in °C and shown in °F; CI is a 95 % moving-block bootstrap interval. MAE debiased and skill, debiased remove the constant offset of the window first, so a station that the model always reads a degree too warm is not scored as if it had no skill — compare the two skill columns to see how much of the error is a fixed offset. n QC next to n counts days whose observation carries a QC flag.

VariableInitMethod Windown MAE °F MAE debiased Bias °F RMSE °F ±1 °F±2 °F±3 °F Skill Skill, debiased Period
tmax00Zbilinear30d26 1 QC3.28 [2.86, 3.76]2.47-2.68 [-3.36, -2.13]3.89 [3.38, 4.43]19% [10%, 29%]31%42%+0.46+0.582026-08-03 → 2026-08-30
tmax00Zbilinear90d26 1 QC3.28 [2.83, 3.85]2.47-2.68 [-3.48, -2.10]3.89 [3.36, 4.47]19% [8%, 30%]31%42%+0.46+0.582026-08-03 → 2026-08-30
tmax00Zbilinear365d32 1 QC3.20 [2.76, 3.71]2.14-2.72 [-3.42, -2.21]3.74 [3.14, 4.31]16% [6%, 26%]31%44%+0.47+0.642026-01-03 → 2026-08-30
tmax00Zbilinearall32 1 QC3.20 [2.80, 3.69]2.14-2.72 [-3.35, -2.16]3.74 [3.22, 4.30]16% [6%, 26%]31%44%+0.47+0.642026-01-03 → 2026-08-30
tmax00Znearest30d26 1 QC3.25 [2.83, 3.74]2.42-2.73 [-3.35, -2.19]3.90 [3.39, 4.44]15% [7%, 24%]35%42%+0.46+0.592026-08-03 → 2026-08-30
tmax00Znearest90d26 1 QC3.25 [2.79, 3.83]2.42-2.73 [-3.49, -2.17]3.90 [3.37, 4.46]15% [7%, 25%]35%42%+0.46+0.592026-08-03 → 2026-08-30
tmax00Znearest365d32 1 QC3.11 [2.62, 3.65]2.12-2.68 [-3.34, -2.20]3.69 [3.04, 4.28]12% [5%, 21%]34%50%+0.49+0.652026-01-03 → 2026-08-30
tmax00Znearestall32 1 QC3.11 [2.64, 3.62]2.12-2.68 [-3.31, -2.16]3.69 [3.09, 4.31]12% [5%, 21%]34%50%+0.49+0.652026-01-03 → 2026-08-30
tmax12Zbilinear30d26 1 QC3.03 [2.60, 3.54]2.27-2.67 [-3.31, -2.13]3.71 [3.21, 4.23]23% [14%, 33%]42%42%+0.51+0.622026-08-03 → 2026-08-30
tmax12Zbilinear90d26 1 QC3.03 [2.55, 3.69]2.27-2.67 [-3.48, -2.10]3.71 [3.14, 4.35]23% [12%, 33%]42%42%+0.51+0.622026-08-03 → 2026-08-30
tmax12Zbilinear365d31 1 QC2.91 [2.44, 3.49]2.00-2.60 [-3.31, -2.09]3.53 [2.87, 4.17]19% [8%, 30%]39%48%+0.51+0.662026-01-03 → 2026-08-30
tmax12Zbilinearall31 1 QC2.91 [2.41, 3.50]2.00-2.60 [-3.30, -2.08]3.53 [2.85, 4.18]19% [8%, 30%]39%48%+0.51+0.662026-01-03 → 2026-08-30
tmax12Znearest30d26 1 QC3.04 [2.62, 3.53]2.23-2.70 [-3.33, -2.17]3.72 [3.24, 4.22]27% [15%, 36%]38%42%+0.50+0.632026-08-03 → 2026-08-30
tmax12Znearest90d26 1 QC3.04 [2.62, 3.67]2.23-2.70 [-3.51, -2.18]3.72 [3.19, 4.34]27% [14%, 36%]38%42%+0.50+0.632026-08-03 → 2026-08-30
tmax12Znearest365d31 1 QC2.85 [2.32, 3.46]2.00-2.57 [-3.21, -2.05]3.49 [2.76, 4.15]23% [7%, 33%]42%52%+0.52+0.662026-01-03 → 2026-08-30
tmax12Znearestall31 1 QC2.85 [2.27, 3.46]2.00-2.57 [-3.28, -1.99]3.49 [2.72, 4.16]23% [8%, 33%]42%52%+0.52+0.662026-01-03 → 2026-08-30
tmin00Zbilinear30d26 1 QC1.67 [1.24, 2.23]1.67-0.28 [-1.11, 0.42]2.11 [1.58, 2.68]42% [25%, 57%]65%88%+0.38+0.382026-08-03 → 2026-08-30
tmin00Zbilinear90d26 1 QC1.67 [1.22, 2.40]1.67-0.28 [-1.39, 0.56]2.11 [1.51, 2.91]42% [23%, 58%]65%88%+0.38+0.382026-08-03 → 2026-08-30
tmin00Zbilinear365d32 1 QC1.81 [1.35, 2.47]1.78-0.44 [-1.53, 0.38]2.21 [1.69, 2.87]38% [18%, 54%]59%84%+0.47+0.502026-01-03 → 2026-08-30
tmin00Zbilinearall32 1 QC1.81 [1.31, 2.46]1.78-0.44 [-1.47, 0.32]2.21 [1.64, 2.89]38% [18%, 55%]59%84%+0.47+0.502026-01-03 → 2026-08-30
tmin00Znearest30d26 1 QC1.63 [1.26, 2.09]1.63-0.01 [-0.80, 0.66]2.02 [1.56, 2.53]46% [29%, 63%]65%88%+0.39+0.392026-08-03 → 2026-08-30
tmin00Znearest90d26 1 QC1.63 [1.23, 2.27]1.63-0.01 [-1.07, 0.82]2.02 [1.50, 2.74]46% [25%, 63%]65%88%+0.39+0.392026-08-03 → 2026-08-30
tmin00Znearest365d32 1 QC1.75 [1.36, 2.31]1.74-0.10 [-1.13, 0.64]2.11 [1.63, 2.69]41% [20%, 58%]56%91%+0.48+0.512026-01-03 → 2026-08-30
tmin00Znearestall32 1 QC1.75 [1.31, 2.30]1.74-0.10 [-1.09, 0.61]2.11 [1.60, 2.71]41% [19%, 59%]56%91%+0.48+0.512026-01-03 → 2026-08-30
tmin12Zbilinear30d26 1 QC1.64 [1.30, 2.10]1.59-0.35 [-1.09, 0.23]2.05 [1.57, 2.66]35% [17%, 50%]65%88%+0.39+0.402026-08-03 → 2026-08-30
tmin12Zbilinear90d26 1 QC1.64 [1.27, 2.32]1.59-0.35 [-1.37, 0.32]2.05 [1.54, 2.91]35% [16%, 50%]65%88%+0.39+0.402026-08-03 → 2026-08-30
tmin12Zbilinear365d31 1 QC1.70 [1.33, 2.26]1.63-0.43 [-1.37, 0.28]2.09 [1.60, 2.77]32% [15%, 47%]65%87%+0.47+0.502026-01-03 → 2026-08-30
tmin12Zbilinearall31 1 QC1.70 [1.34, 2.25]1.63-0.43 [-1.35, 0.22]2.09 [1.62, 2.79]32% [15%, 48%]65%87%+0.47+0.502026-01-03 → 2026-08-30
tmin12Znearest30d26 1 QC1.55 [1.22, 1.97]1.54-0.09 [-0.81, 0.49]1.97 [1.55, 2.52]50% [36%, 63%]65%88%+0.42+0.422026-08-03 → 2026-08-30
tmin12Znearest90d26 1 QC1.55 [1.21, 2.20]1.54-0.09 [-1.09, 0.59]1.97 [1.50, 2.74]50% [33%, 63%]65%88%+0.42+0.422026-08-03 → 2026-08-30
tmin12Znearest365d31 1 QC1.61 [1.26, 2.15]1.59-0.10 [-0.98, 0.57]2.00 [1.58, 2.62]45% [26%, 59%]61%90%+0.50+0.522026-01-03 → 2026-08-30
tmin12Znearestall31 1 QC1.61 [1.24, 2.13]1.59-0.10 [-0.98, 0.50]2.00 [1.56, 2.61]45% [25%, 61%]61%90%+0.50+0.522026-01-03 → 2026-08-30

+ model too warm · − model too cold · bias interval includes zero · ★ lowest MAE · = not distinguishable from the leader · ▼ significantly worse · n < 30 greyed and unranked · CI is a 95 % moving-block bootstrap interval.

Daily error, last 90 days

Daily forecast minus observed error in °F for GraphCast (IFS init) at KBOS, lead day 2, 00Z bilinear tmax+10+50-5-102026-08-03: +0.65 °F2026-08-04: -4.71 °F2026-08-05: -4.68 °F2026-08-06: +1.5 °F2026-08-07: -5.08 °F2026-08-08: -4.24 °F2026-08-09: +0.18 °F2026-08-10: +0.89 °F2026-08-11: -3.28 °F2026-08-12: -2.68 °F2026-08-13: -3.36 °F2026-08-14: -4.57 °F2026-08-15: -1.08 °F2026-08-16: -4.69 °F2026-08-17: -4.21 °F2026-08-18: -0.07 °F2026-08-19: -7.27 °F2026-08-20: -4.39 °F2026-08-21: +2.07 °F2026-08-22: -1.31 °F2026-08-23: +2.19 °F2026-08-24: -7.56 °F2026-08-25: -4.02 °F2026-08-26: +0.27 °F2026-08-27: -6.15 °F2026-08-30: -4.09 °F2026-08-032026-08-30°F, forecast − observed
Forecast − observed, °F, 00Z bilinear daily maximum. The dashed line is zero; the thick line is a centred 7-day mean, drawn only where the whole window is present. Gaps are days with no score, never interpolation. Hover a point for its date and value.
The same series as a table (28 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-4.09
2026-08-29—
2026-08-28—
2026-08-27-6.15
2026-08-26+0.27
2026-08-25-4.02
2026-08-24-7.56
2026-08-23+2.19
2026-08-22-1.31
2026-08-21+2.07
2026-08-20-4.39
2026-08-19-7.27
2026-08-18-0.07
2026-08-17-4.21
2026-08-16-4.69
2026-08-15-1.08
2026-08-14-4.57
2026-08-13-3.36
2026-08-12-2.68
2026-08-11-3.28
2026-08-10+0.89
2026-08-09+0.18
2026-08-08-4.24
2026-08-07-5.08
2026-08-06+1.50
2026-08-05-4.68
2026-08-04-4.71
2026-08-03+0.65

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KBOS, lead day 2-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 2 days-7 to -6 °F: 1 day-6 to -5 °F: 1 day-5 to -4 °F: 10 days-4 to -3 °F: 4 days-3 to -2 °F: 2 days-2 to -1 °F: 4 days-1 to 0 °F: 1 day0 to 1 °F: 4 days1 to 2 °F: 1 day2 to 3 °F: 2 days3 to 4 °F: 0 days4 to 5 °F: 0 days5 to 6 °F: 0 days6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 3.28 · P90 |e| 5.04 °F-100+10 °Fn = 32 days
All scored days for 00Z bilinear daily maximum, 20 equal bins. The dashed marks are the 50th and 90th percentiles of the absolute error, mirrored on both sides. Hover a bar for its bin and count.
Bin counts as a table
From °FTo °FDays
-10.00-9.000
-9.00-8.000
-8.00-7.002
-7.00-6.001
-6.00-5.001
-5.00-4.0010
-4.00-3.004
-3.00-2.002
-2.00-1.004
-1.00+0.001
+0.00+1.004
+1.00+2.001
+2.00+3.002
+3.00+4.000
+4.00+5.000
+5.00+6.000
+6.00+7.000
+7.00+8.000
+8.00+9.000
+9.00+10.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08263.28 -2.68
2026-0162.88 -2.88

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 31
GraphCast (IFS init)2026-01-03 → 2026-08-30 31

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means GraphCast (IFS init) has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 26 -0.19 [-1.11, 0.48] no
Aurora (IFS init) 1 -0.03 [-0.03, -0.03] yes
FourCastNet v2 (IFS init) 1 -2.00 [-2.00, -2.00] yes
NCEP GFS 26 +0.45 [-0.70, 1.48] no
ECMWF IFS HRES 20 +0.87 [-0.24, 2.00] no
Pangu-Weather (IFS init) 1 +0.25 [0.25, 0.25] yes
Persistence (baseline) 25 -2.76 [-5.44, -0.64] yes

Cite this page

ShortCastCheck, KBOS graphcast_ifs lead 2, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KBOS/model/graphcast_ifs/lead/2/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KBOS (Boston Logan), model graphcast_ifs, lead day 2. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KBOS/model/graphcast_ifs/lead/2/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

JSON CSV all scores methodology v0.2 licence